This invention relates to coating compositions based on a water-borne reaction product of a carboxyl-functional polymer, a modified epoxide, and a tertiary amine, having general utility in coating metallic and paper substrates. It is more particularly directed to coating compositions useful as automotive and can coatings.
Coatings of the prior art are often dissolved or dispersed in organic solvents. Among commonly utilized thermosetting compositions are those based on epoxy resins crosslinked with nitrogen resins, usually in an acid catalyzed process.
Increased awareness of the environmental hazards of allowing organic solvent vapors to enter the atmosphere, the desirability of a single system that can be applied not only by the more conventional techniques of spray, roller or flow coating but also by electrodeposition, and the economy resulting from the substitution of water for some or all of the solvents in a coating composition, are all factors mitigating in favor of water-borne coating compositions.
Aqueous epoxy-acrylic-amine coating compositions of other investigators, including U.S. Pat. Nos. 3,969,300--Nagata (1976) and 4,021,396--Wu (1977) are less stable than desired or lack advantages of the present invention.
The composition of this invention is an aqueous solution or dispersion of the reaction product of a carboxyl-functional polymer, a modified terminally functional epoxy resin with at least some of its epoxide groups converted to esters, ethers or phenolic hydroxy groups, and a tertiary amine. Such a water-borne system can optionally contain a crosslinking agent, is stable, and can be applied to metallic substrates by spray, roller, dip or flow coating or by electrodeposition at the anode and to paper.